The typical inks used in the flexographic printing industry must be mixed with a solvent, such as alcohol or water, to form a usable ink solution with an acceptable viscosity. Because the solvents are so volatile, evaporating to the atmosphere, solvent must be continuously added to the ink solution to maintain the desired viscosity.
Different control apparatus have been developed in an attempt to maintain a solution at a desired viscosity. U.S. Pat. No. 3,557,817 issued on Jan. 26, 1971 to Edwin H. Royse discloses one apparatus for mixing fluids of different specific gravity to maintain a solution with the desired properties. U.S. Pat. No. 3,848,618 issued Nov. 19, 1974 to Edwin H. Royse discloses another device for mixing fluids of different specific gravities to maintain a solution of desired properties.
While the devices previously designed, including those disclosed in the patents above, are satisfactory in many aspects, a need still exists for an improved control system for maintaining the viscosity of an ink solution within the desired range. A critical consideration is the difficulty in maintaining such a control system. A complex and multicomponent system can often require excessive time for cleaning and maintenance, compromising the very purpose for the control system to eliminate labor intensive maintenance.